Reductive methylation of membrane proteins in human erythrocyte ghosts

The first demonstration of a method to incorporate radiolabeled methyl groups from [14C]formaldehyde into membrane proteins in human erythrocytes by reductive methylation in the presence of NaCNBH3 is described. This method is based on the work of Jentoft and Dearborn [(1979) J. Biol. Chem. 254, 4359-4365], who demonstrated the feasibility of this procedure in soluble proteins. The results of the present study suggest that cytoskeletal protein components of erythrocyte membranes are primarily labeled and that this procedure provides a useful method to investigate the structure of membrane proteins.